[NEW YORK] US consumers wasted billions of dollars last year filling their cars with costly premium-grade petrol for no tangible benefit, according to a study by the country's leading motorist advocacy group.
The report by Heathrow, Florida-based AAA comes as low pump prices and a growing economy enticed US motorists to buy more premium-grade petrol in June than in any month since 2003, according to the US Energy Information Administration.
While an overwhelming majority of cars on US roadways are designed to consume regular petrol, the study found that motorists still use premium-grade in the hopes of achieving more horsepower and better fuel economy.
As a result, US drivers spent an estimated US$2.1 billion extra by using premium petrol in vehicles designed for regular fuel.
Premium provides little or no benefit to cars designed to run on lower octane, regular petrol, the study said.
"Drivers see the 'premium' name at the pump and may assume the fuel is better for their vehicle," John Nielsen, AAA's managing director of automotive engineering and repair, said in a statement.
"AAA cautions drivers that premium petrol is higher octane, not higher quality, and urges drivers to follow the owner's manual recommendations for their vehicle's fuel."
What distinguishes premium from other grades is its increased ability - expressed in octane - to resist premature detonation, or knocking, as it is compressed in the engine before ignition.
Premium petrol is used in high-compression engines so it is often associated with high-performance sportscars or luxury vehicles. Last week, a gallon of premium petrol was selling on average 48 cents higher than regular petrol, among the widest spreads since 1994, EIA data shows.
Refiners such as Royal Dutch Shell have focused on premium petrol sales due to healthy margins and its rising popularity.
In June, 45.3 million gallons of premium petrol was sold, the most in any month since 2003, according to EIA.
Sales of premium petrol, which make up less than 15 per cent of US petrol sales, have increased at a faster rate than sales of regular gasoline in recent years.
AAA tested 87-octane (regular) and 93-octane (premium) petrol in vehicles with a V-8, V-6 or I4 engine designed for regular-grade fuel. The testing found no significant increases in horsepower and fuel efficiency.
The survey found that 70 per cent of US drivers own a car requiring regular petrol, while 16 per cent drive cars that require premium fuel. The remaining 14 per cent require mid-grade petrol or an alternative source.